/*
 * The Minimal snprintf() implementation
 *
 * Copyright (c) 2013,2014 Michal Ludvig <michal@logix.cz>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *     * Neither the name of the auhor nor the names of its contributors
 *       may be used to endorse or promote products derived from this software
 *       without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * ----
 *
 * This is a minimal snprintf() implementation optimised
 * for embedded systems with a very limited program memory.
 * mini_snprintf() doesn't support _all_ the formatting
 * the glibc does but on the other hand is a lot smaller.
 * Here are some numbers from my STM32 project (.bin file size):
 *      no snprintf():      10768 bytes
 *      mini snprintf():    11420 bytes     (+  652 bytes)
 *      glibc snprintf():   34860 bytes     (+24092 bytes)
 * Wasting nearly 24kB of memory just for snprintf() on
 * a chip with 32kB flash is crazy. Use mini_snprintf() instead.
 *
 */

#include "mini-printf.h"

static unsigned int
mini_strlen(const char *s)
{
    unsigned int len = 0;
    while (s[len] != '\0')
        len++;
    return len;
}

float simple_pow(float base, int exponent)
{
    float result = 1.0;
    int abs_exponent = exponent < 0 ? -exponent : exponent;

    for (int i = 0; i < abs_exponent; ++i)
    {
        result *= base;
    }

    if (exponent < 0)
    {
        result = 1.0 / result;
    }

    return result;
}

static unsigned int
mini_itoa(int value, unsigned int radix, unsigned int uppercase, unsigned int unsig,
          char *buffer, unsigned int zero_pad)
{
    char *pbuffer = buffer;
    int negative = 0;
    unsigned int i, len;

    /* No support for unusual radixes. */
    if (radix > 16)
        return 0;

    if (value < 0 && !unsig)
    {
        negative = 1;
        value = -value;
    }

    /* This builds the string back to front ... */
    do
    {
        int digit = value % radix;
        *(pbuffer++) = (digit < 10 ? '0' + digit : (uppercase ? 'A' : 'a') + digit - 10);
        value /= radix;
    } while (value > 0);

    for (i = (pbuffer - buffer); i < zero_pad; i++)
        *(pbuffer++) = '0';

    if (negative)
        *(pbuffer++) = '-';

    *(pbuffer) = '\0';

    /* ... now we reverse it (could do it recursively but will
     * conserve the stack space) */
    len = (pbuffer - buffer);
    for (i = 0; i < len / 2; i++)
    {
        char j = buffer[i];
        buffer[i] = buffer[len - i - 1];
        buffer[len - i - 1] = j;
    }

    return len;
}

static unsigned int
mini_ftoa(float value, char *buffer, unsigned int zero_pad, unsigned int precision_bit)
{
    int ipart = (int)value;
    float fpart = value - (float)ipart;

    unsigned int ilen = mini_itoa(ipart, 10, 0, 0, buffer, zero_pad);
    unsigned int flen = 0;

    if (precision_bit == 0)
        precision_bit = 3;
    buffer[ilen] = '.';
    fpart = fpart * simple_pow(10, precision_bit);
    flen = mini_itoa((int)fpart, 10, 0, 0, (buffer + ilen + 1), precision_bit);

    return (ilen + 1 + flen);
}

struct mini_buff
{
    char *buffer, *pbuffer;
    unsigned int buffer_len;
};

static int
_putc(int ch, struct mini_buff *b)
{
    if ((unsigned int)((b->pbuffer - b->buffer) + 1) >= b->buffer_len)
        return 0;
    *(b->pbuffer++) = ch;
    *(b->pbuffer) = '\0';
    return 1;
}

static int
_puts(char *s, unsigned int len, struct mini_buff *b)
{
    unsigned int i;

    if (b->buffer_len - (b->pbuffer - b->buffer) - 1 < len)
        len = b->buffer_len - (b->pbuffer - b->buffer) - 1;

    /* Copy to buffer */
    for (i = 0; i < len; i++)
        *(b->pbuffer++) = s[i];
    *(b->pbuffer) = '\0';

    return len;
}

int mini_vsnprintf(char *buffer, unsigned int buffer_len, const char *fmt, va_list va)
{
    struct mini_buff b;
    char bf[128];
    char ch;

    b.buffer = buffer;
    b.pbuffer = buffer;
    b.buffer_len = buffer_len;

    while ((ch = *(fmt++)))
    {
        if ((unsigned int)((b.pbuffer - b.buffer) + 1) >= b.buffer_len)
            break;
        if (ch != '%')
            _putc(ch, &b);
        else
        {
            char zero_pad = 0;
            char precision_bit = 0;
            char *ptr;
            unsigned int len;

            ch = *(fmt++);

            /* Zero padding requested */
            if (ch == '\0')
                goto end;
            if (ch >= '0' && ch <= '9')
            {
                zero_pad = ch - '0';
                ch = *(fmt++);
            }
            if (ch == '.')
            {
                ch = *(fmt++);
                if (ch >= '0' && ch <= '9')
                {
                    precision_bit = ch - '0';
                    ch = *(fmt++);
                }
            }

            switch (ch)
            {
            case 0:
                goto end;

            case 'u':
            case 'd':
                len = mini_itoa(va_arg(va, unsigned int), 10, 0, (ch == 'u'), bf, zero_pad);
                _puts(bf, len, &b);
                break;

            case 'x':
            case 'X':
                len = mini_itoa(va_arg(va, unsigned int), 16, (ch == 'X'), 1, bf, zero_pad);
                _puts(bf, len, &b);
                break;

            case 'c':
                _putc((char)(va_arg(va, int)), &b);
                break;

            case 's':
                ptr = va_arg(va, char *);
                _puts(ptr, mini_strlen(ptr), &b);
                break;

            case 'f':
                len = mini_ftoa(va_arg(va, float), bf, zero_pad, precision_bit);
                _puts(bf, len, &b);
                break;

            default:
                _putc(ch, &b);
                break;
            }
        }
    }
end:
    return b.pbuffer - b.buffer;
}

int mini_snprintf(char *buffer, unsigned int buffer_len, const char *fmt, ...)
{
    int ret;
    va_list va;
    va_start(va, fmt);
    ret = mini_vsnprintf(buffer, buffer_len, fmt, va);
    va_end(va);

    return ret;
}
